The present invention relates generally to “smart” cards and, more particularly, relates to smart cards which have at least one metal layer and are capable of radio frequency transmission (RF) and physical electrical interfacing. In particular, the invention relates to dual interface (i.e., capable of contactless and/or contact operation) smart cards having a metal layer and a rich and aesthetically pleasant appearance.
Smart cards are highly desirable and are in wide use, including: in payment and ticketing applications, such as mass transit and motorway tolls; in personal identification and entitlement schemes on regional, national, and international levels; in citizen cards; in drivers' licenses; in patient card schemes; and in biometric passports to enhance security for international travel.
A smart card is a card that includes embedded electronic circuitry such as an integrated circuit (IC) chip that can be either: (a) a secure microcontroller, also referred to as a microprocessor, or equivalent intelligence device with internal memory; or (b) a memory chip alone. A smart card connects or couples to a card reader with direct physical contact and/or with a remote contactless radio frequency interface.
There are three general categories of smart cards of interest. They are referred to herein as (1) contact, (2) contactless and (3) dual interface. (1) A “contact” smart card includes an IC chip connected to a conductive contact plate on which are mounted a number of physical contact pads (typically gold plated) located generally on the top surface of the card. A contact smart card must be inserted into a contact type smart card reader and transmission of commands, data, and card status takes place over the physical contact pads. (2) A “contactless” smartcard contains an IC chip and a card antenna by means of which RF signals are coupled between the smart card's chip and the antenna of a card reader. This permits wireless (e.g., RF) communication between the card and a card reader with no direct electrical contact between the card and the card reader. A contactless smart card requires only close proximity to a reader. Both the reader and the smart card have antennae, and the two communicate using radio frequencies (RF) over a contactless link. Most contactless cards also derive power for the internal chip from electromagnetic signals emitted by the card reader. The range of operation may vary from less than an inch to several inches. (3) A “dual-interface” smart card has, typically, a single IC chip (but could have two) and includes both contact and contactless interfaces. With dual-interface cards, it is possible to access the IC chip(s) using a contact and/or a contactless interface.
It is desirable to make dual interface smart cards which can provide “contactless” and/or “contact” capability. It has also become very desirable and fashionable to make cards with one or more metal layers. A metal layer provides a desirable weight and a decorative pattern and/or reflective surface enhancing the card's appearance and aesthetic value. This is especially desirable for use by high-end customers. It is therefore desirable to make dual interface (contacts and contactless) smart cards having a metal layer.
However, several problems arise in the making of dual interface (“contactless” and “contact”) smart cards with a metal layer because of conflicting requirements. By way of example, to construct a dual interface smart card, the contact pads associated with the IC chip need to be located along an external surface (top or bottom, but normally top) of the card to make contact with a contact card reader and the IC chip will generally be located near the top surface. However, any metal layer in the card interferes with radio-frequency (RF) communication signals (e.g., attenuates) between the card and the reader, and this could render the contactless smart card useless. So, a dual interface smart card with a metal layer needs to solve the problem of RF interference with respect to the IC chip. Compounding the problem is the requirement that the dual interface metal smart card have a highly sophisticated appearance. Due to the prestige and aesthetic aspect of these cards it is desirable that there be no perceptible depression or bump along the surface of the card, except for the contact pads.